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Day: 20120725

ScienceDaily (July 24, 2012) — Neuroscientists from Wayne State University and the Massachusetts Institute of Technology (MIT) are taking a deeper look into how the brain mechanisms for memory retrieval differ between adults and children. While the memory systems are the same in many ways, the researchers have learned that crucial functions with relevance to learning and education differ.

The team’s findings were published on July 17, 2012, in the Journal of Neuroscience.

According to lead author Noa Ofen, Ph.D., assistant professor in WSU’s Institute of Gerontology and Department of Pediatrics, cognitive ability, including the ability to learn and remember new information, dramatically changes between childhood and adulthood. This ability parallels with dramatic changes that occur in the structure and function of the brain during these periods.

In the study, “The Development of Brain Systems Associated with Successful Memory Retrieval of Scenes,” Ofen and her collaborative team tested the development of neural underpinnings of memory from childhood to young adulthood. The team of researchers exposed participants to pictures of scenes and then showed them the same scenes mixed with new ones and asked them to judge whether each picture was presented earlier. Participants made retrieval judgments while researchers collected images of their brains with magnetic resonance imaging (MRI).

Using this method, the researchers were able to see how the brain remembers. “Our results suggest that cortical regions related to attentional or strategic control show the greatest developmental changes for memory retrieval,” said Ofen.

The researchers said that older participants used the cortical regions more than younger participants when correctly retrieving past experiences.

“We were interested to see whether there are changes in the connectivity of regions in the brain that support memory retrieval,” Ofen added. “We found changes in connectivity of memory-related regions. In particular, the developmental change in connectivity between regions was profound even without a developmental change in the recruitment of those regions, suggesting that functional brain connectivity is an important aspect of developmental changes in the brain.”

This study marks the first time that the development of connectivity within memory systems in the brain has been tested, and the results suggest that the brain continues to rearrange connections to achieve adult-like performance during development.

Ofen and her research team plan to continue research in this area, focused on modeling brain network connectivity, and applying these methods to study abnormal brain development.

Wayne State University – Office of the Vice President for Research (2012, July 24). Better understanding of memory retrieval between children and adults. ScienceDaily. Retrieved July 26, 2012, from http://www.sciencedaily.com­ /releases/2012/07/120724115105.htm

ScienceDaily (July 23, 2012) — How quickly can new species arise? In as little as 6,000 years, according to a study of Australian sea stars.

“That’s unbelievably fast compared to most organisms,” said Rick Grosberg, professor of evolution and ecology at UC Davis and coauthor on the paper published July 18 in the journal Proceedings of the Royal Society B.

Grosberg is interested in how new species arise in the ocean. On land, groups of plants and animals can be physically isolated by mountains or rivers and then diverge until they can no longer interbreed even if they meet again. But how does this isolation happen in the wide-open ocean?

Grosberg and colleagues studied two closely related “cushion stars,” Cryptasperina pentagona and C. hystera, living on the Australian coast. The animals are identical in appearance but live in different regions: Hystera occurs on a few beaches and islands at the far southern end of the range of pentagona.

And their sex lives are very, very different. Pentagona has male and female individuals that release sperm and eggs into the water where they fertilize, grow into larvae and float around in the plankton for a few months before settling down and developing into adult sea stars.

Hystera are hermaphrodites that brood their young internally and give birth to miniature sea stars ready to grow to adulthood.

“It’s as dramatic a difference in life history as in any group of organisms,” Grosberg said.

The researchers looked at the diversity in DNA sequences from sea stars of both species and estimated the length of time since the species diverged.

The results show that the species separated about 6,000 to 22,000 years ago. That rules out some ways new species could evolve. For example, they clearly did not diverge slowly with genetic changes over a long period of time, but were isolated quickly.

Over the last 11,000 years, the boundary between cold and warm water in the Coral Sea has fluctuated north and south. A small population of the ancestral sea stars, perhaps even one individual, might have colonized a remote area at the southern end of the range then been isolated by one of these changes in ocean currents.

Other authors on the paper are: Jonathan Puritz and Robert Toonen, University of Hawaii; at Simon Fraser University in British Columbia, Canada Michael Hart and Carson Keever, who earned his undergraduate degree from UC Davis; Jason Addison, University of New Brunswick, Canada (previously a postdoctoral researcher at UC Davis); and Maria Byrne, University of Sydney.

The work was supported by a grant from the National Science Foundation to Grosberg and Toonen, a former UC Davis graduate student.